Electromagnetic indicator

ABSTRACT

A two position indicating device including an indicator member in the form of a rotor that carries a single permanent magnet and is mounted for rotation between two limit positions which are determined by engagement of spaced-apart portions of the rotor with the end of a pole piece of a stationary electromagnet structure. The electromagnet structure comprises a combined bobbin and rotor support, the rotor support having two spaced ears and the rotor being rotatably mounted to the spaced ears by detent means comprising a hole in each ear and two pins carried by the rotor. Attachment and removal of the rotor is achieved by flexing the two ears apart far enough to release the two rotor pins. A coil is wound around the bobbin and terminal means are provided for energizing the coil to selectively establish first and second electromagnetic fields of opposite orientation for effecting movement of the rotor between its two limit positions.

United States Patent Pihl 51 July 18, 1972 Primary Examiner-Hamld Bmome[72] Inventor: George E. Pihl, Abington, Mass. Attorney-Robert Schilleret [73] Assignee: Miniature Electronic Components Corp., ABSTRACTHolbrook Mass A two position indicating device including an indicator[22] Filed: Au 27, 1971 member in the form of a rotor that carries asingle ermanent 8 P magnet and is mounted for rotation between two limitposi- [21] Appl' 175552 tions which are determined by engagement ofspaced-apart portions of the rotor with the end of a pole piece of astationa- 52 us. Cl. .335/234, 335/273, 340/373 W electmmagfletStructure The electwmaflnet [51] Int. Cl. ..H0lf 7/08 prises a combinedbbbin and support the rotor Support 58 Field of Search ..335/234 272 28117- having spaced and being mmably mum! 2 to the spaced ears by detentmeans comprising a hole in each ear and two pins carried by the rotor.Attachment and [56] References Cited removal of the rotor is achieved byflexing the two ears apart far enough to release the two rotor pins. Acoil is wound UNITED STATES PATENTS around the bobbin and terminal meansare provided for energizing the coil to selectively establish first andsecond elec- 2,4l5,452 2/1947 Taylor et al ..340/373 tromagnefic fieldsof opposite orientation for effecting move 3,025 ,5 l 2 3/1962 Bloechl..340/373 men! ofthe rotor between its two limit positimm 3,430,] 702/1969 Shatas et al ..335/234 l2 Claim, 5 Drawing Figures PATENTED JUL!8 I972 SHEET 2 UF 2 T] III GEORGE E. P/HL //V VE/VTOR.

pana iacia POWER SOURCE;

ATTORNEYS ELECTROMAGNETIC INDICATOR This invention relates to miniatureelectromagnetic indicators and more particularly to provision of lowcost indicators capable of indicating two different predeterminedconditions. The present invention is an inprovement over electromagneticindicators of the type setforth in US. Pat. No. 3,451,055 and U.S. Pat.Nos. 3,364,481, 2,415,452, and 3,430,170.

OBJECTS AND SUMMARY OF THE INVENTION The primary object of thisinvention is to provide a new miniature electromagnetic indicatorcapable of binary indication that satisfies the myriad of requirementsthat exist in the commercial and industrial fields by offeringreliability combined with low cost.

A further object of the invention is to provide a quick acting miniaturebi-stable electromagnetic indicator that is selflatching in both of itstwo display positions, whereby the indicator may be used as a faultisolation indicator or a condition monitoring device for electrical andelectromechanical systems. Still another object of the invention is toprovide a low cost indicator that is moisture sealed, can be made insizes as small as 0.250 X 0.375 X 0.800 inches, may be pulse operatedand will withstand steady state power at elevated temperatures.

A further object of the invention is to provide an indicator having amovable indicator member that provides an indicia display that is highlyvisible and which can be seen when viewed at different angles. In apreferred embodiment of the invention the foregoing and other objectsare achieved by a construction which comprises a plastic indicatorhousing that is transparent at one end so as to permit viewing of thedisplayed indicia of the indicator member. Contained within the case isan electromagnetic structure comprising a combined rotor support andhollow bobbin, a core made of magnetic material disposed within thebobbin, and a coil wound around the bobbin. The rotor support comprisesa pair of flexible ears formed integral with one end of the bobbin andhaving a pair of aligned holes for use in mounting the indicator member.The indicator member is a rotor having salient permanent magnet polesand a pair of aligned pins that are sized to fit within the holes formedin the two ears. The rotor further includes a slot in its periphery,with one end of the pole piece extending into the slot and with the slothaving end walls that determine, by engagement with the pole piece, twolimit positions for the rotor. The rotor has two distinct indicia, oneof which is displayed when the rotor is in one limit position and theother is displayed when the rotor is in its other limit position.Movement of the rotor is effected by energizing the coil so as tomagnetize the pole piece with a polarity such that the pole piece willmagnetically influence the rotor to rotate on its axis. Attraction ofthe pole piece to one of the salient permanent magnet poles of the rotoracts to magnetically latch the rotor so as to maintain a steady stateindication.

Other features and advantages of the present invention are set forth inor rendered obvious by the following detailed specification which is tobe considered together with the accompanying drawings.

THE DRAWINGS FIG. 1 is an exploded view in perspective of a preferredembodement of the invention;

FIG. 2 is a longitudinal, partial sectional, view of one embodiment ofthe invention;

FIG. 3 is a perspective view of the assembled indicator; FIG. 4 is anexploded view of the rotor, i.e. indicator member; and

FIG. 5 schematically illustrates an operating circuit for the indicator.

DESCRIPTION OF PREFERRED EMBODIMENT Turning now to FIGS. 1 and 2, thepreferred embodiment of the invention comprises a case 2 that is made ofa strong transparent plastic material, e.g. Lexan. The case is generallyrectangular in cross-section, comprising a pair of relatively the case 2may be transparent from one end to the other, it is preferred that theside walls and the top and bottom walls be rendered opaque and thecurved end wall 12 and the bevelled faces 14 and 16 be transparent asillustrated. The case may be made opaque by coating it with aheat-resistant paint 17 or by other methods known to persons skilled inthe art. Use of a fully transparent case may be tolerated where theindicator is mounted in a mounting panel so that only the curved suracel2 and the bevelled faces 14 and 16 protrude from the panel and arevisible to the observer.

Referring again to FIGS. 1 and 2, the indicator comprises a combinedbobbin and rotor support identified generally at 18. This element of theindicator is made of an electrically insulating material, preferably aplastic material such as nylon reinforced with glass fibers. The element18 comprises a shaft-like portion 22 of rectangular cross section, witha rectangular flange 24 formed at one end and a rectangular end wall orflange 26 formed at its opposite end. The shaft-like section 22 ishollow, having an axial passageway 27 of rectangular crosssection thatextends through the flanges 24 and 26 as shown. The flanges 24 and 26and the shaft-like portion 22 together form a bobbin on which is woundan operating coil 28 as hereinafter described. Additionally, the endwall or flange 26 forms part of the rotor support. In this connection itis to be noted that two like ears 30 and 32 are formed integral with thewall 26 at its broadest sides. The end wall 26 also is enlarged at twosides as shown at 34 so as to provide reinforcement for it and the twoears. The two ears are each provided with round holes 36. These holesare aligned with each other and are located at a point remote from theend wall 26. It is to be noted that end wall 26 and the two earsessentially form a U- shaped yoke. The mutually confronting surfaces ofthe two ears are fonned with like ribs 40 that extend parallel to theshaft-like section 22. The holes 36 extend through these ribs. The ribsprovide reinforcement for the two ears and also act as bearing surfacesfor the rotor.

An elongate core member 44 is mounted within the combined bobbin androtor support 18. This core member is made of a magnetic material suchas soft iron. A preferred material is that sold commercially under thetrademark NIRON. The core member has a rectangular cross section similarto the cross-sectional configuration of the interior of the bobbin andis sized so as to make a snug fit within the passageway 27. As shown inFIG. 2, one end of the core member preferably terrninates just short ofthe outer end surface of the flange 24, while the opposite end of thecore member extends between the two ears and stops short of the holes36. This end of the core member is twisted as shown at 46 so that thebroader sides 48 thereof extend parallel to the axes of the two holes36.

The indicator element of the indicator is a rotor as shown at 50. Thisrotor is formed of two identical complementary parts 52 and 54 that aremade of plastic, e.g. Lexan. Each of the parts is essentiallysemi-circular, comprising a circularly curved or arcuate surface 56,flat side surfaces 58 and 60, and a flat diametrically extending surface62. Each of the two rotor parts is provided with a cavity 64 of squarecross section, the cavity extending radially and at a right angle to thediametrically extending surface 62. Additionally, each of the rotorparts is provided with an arcuate slot 66 at its periphery, the arcuateslot commencing at the diametrically extending surface 62 andterminating just short of the cavity 64. The width of the slots 66,i.e., the distance between its side walls, is greater than the width ofthe broad surfaces 48 of the core member. Each of the rotor parts isalso formed with a pin unit at one side, the pin unit comprising a shortpin 68 and an enlarged round flange 70. The center axis of pin 68 andflange 70 is the center of curvature of surface 56. The two rotor partsfit together so that the slots 66 form one continuous slot and thecavities 64 form one continuous cavity. When the rotor is beingassembled, a permanent magnet 72 having salient poles at its oppositeends is disposed within the cavities 64.

The assembled rotor 50 is mounted in the device by flexing the two carsapart just enough to permit the pins 68 to be slipped into the holes 36.The inherent resiliency of the two ears maintains the bearing surface ofribs 40 against the flanges 70 and thereby limits translational movementof the rotor along the axis of the pins while permitting it to rotate.As seen in FIG. 2, the rotor is mounted between the two ears as abovedescribed so that the slot 66 faces the core member 44, with the twistedend of the core member extending into the slot 66 but spaced from thesides and base of the slot so as to permit the rotor to rotate freely onits axis. However, the twisted end of the core member can intercept theend surfaces 74 and 76 of the slots 66 when the rotor is rotated.Accordingly, rotation of the rotor is limited between first and secondlimit postions that are determined by engagement of its slot surfaceswiththe core member. The assembled rotor is adapted to indicate onestate or another according to whether it is in one orthe other of itstwo' limit positions. The binary indication may be achieved by means ofany suitable indicia. Preferably the binary indication is achieved bymaking the two rotor parts of contrasting colors. Preferably one of theparts 52 and 54 is black and the other is white. Since these parts aremade of plastic, the coloring agents may be embodied in the plasticmolding compound. Alternatively, the parts may be colored by paintingthem.

Completing the indicator is a printed circuit tabbing board 78 made ofan electrical insulating material and having a pair of notches 80 and 82at opposite sides and a pair of conductive lands 86 and 88 on one face.These lands serve as connecting points for the ends of the coil 28 and apair of tenninal leads 90 and 92. The tabbing board is mounted in thecase 2 against the flange 24 of the combined bobbin and rotor support18, with the conductive lands facing away from the flange 24.

The above described indicator is easily assembled. One mode of assemblyis as follows. First the rotor is assembled by cementing its two parts52 and 54 together with the magnet 72 captivated between them as shown.Then the core 44 is inserted in passageway 27. The core is secured inplace in the bobbin. This may be done by sizing the core so that itmakes a force fit in hole 27 Preferably, however, it is cemented inplace. Then the tabbing board 78 is cemented to the flange 24 of thecombined bobbin and rotor support 18 and the coil 28 is wound on thebobbin. The two ends of the coil are lead through the notches 80 and 82and soldered or welded to the lands 86 and 88. It is to be noted thatthe short sides of flange 24 may be provided with short notches as shownat 94 in FIG. 1 to facilitate leading the ends of the coil through thenotches 80 and 82 to the conductive lands. Then the rotor is mounted tothe combined bobbin and rotor support 18 by flexing the ears 30 and 32apart far enough to permit the pins 68 to be inserted in holes 36.Preferably one part of the rotor is white and the other is black.Thereafter the foregoing assembly is inserted in the case 2. The extentto which the assembly can be inserted in the case is limited byengagement of the ears 30 and 32 with the inside surfaces of thebevelled faces 14 and 16. The length of the ears and the angle ofinclination of the bevelled faces is such that as seen in FIG. 1, theassembly cannot be inserted far enough for the rotor to engage theinside surfaces of the curved end wall 12 and the bevelled faces 14 and16. In practice the assembly is insertable far enough to leave aboutone-sixteenth to one-eighth inch clearance between the rotor and thecurved end wall and the sides of the rotor have a minimum clearance ofabout the same magnitude with respect to the inside surfaces of thebevelled faces of the case. Before the assembly has been inserted,terminal pins 90 and 92 are secured by welding or soldering to the lands86 and 88 respectively. A potting compound as'shown at 96 is appliedover the tabbing board to reinforce the terminal pins and lock theassembly in place. The potting compound may be an epoxy resin and alsoserves to hermetically seal off the interior of the case 2.

A typical operating circuit for the indicator is shown in FIG. 5. Thiscircuit comprises a DC power source 98 and two reversing switches 100and 102. The latter may be conventional single-pole, double throwswitches with their pole terminals connected to the positive andnegative sides of the power source as shown. The two contact terminalsof switches 100 and 102 are identified by numerals 104 and 106. Contact104 of switch 100 and contact 106 of switch 102 are connected toterminal pin 90, while contacts 106 of switch 100 and contacts 104 ofswitch 102 are connected to terminal pin 92. The moveable contacts ofthe two switches are ganged together so as to close on contact terminals104 and 106 of switches 100 and 102 simultaneously or on contacttemrinals 106 and 104 of switches 100 and 102 simultaneously.

Operation of the indicator is straightforward. Assume that the switchesare positioned as shown in FIG. 5 and that the rotor is positioned sothat its north pole is nearest to the core 44 and the black surface ofthe rotor is visible through the front end of the case. lfnow theswitches are reversed, current will flow through the coil in onedirection to establish a magnetic field which magnetizes the pole pieceso that its twisted end is a north pole. When this occurs the north poleof the rotor magnet is repelled and the rotor is caused to rotate untilits south pole is nearest to the pole piece and its white surface isvisible through the front end of the case. If subsequently the switchesare again reversed, the resulting magnetic field will magnetize the polepiece so that its twisted end becomes a south pole. When this occurs,the south pole of the rotor magnet is repelled and the rotor will returnto its original position to again provide a black display. It is notnecessary to maintain current through the coil to maintain a currentdisplay. If the power source is turned off, the rotor will hold itsposition due to the attraction of the pole piece for the adjacent poleof the rotors magnet.

An advantage of the unit is that it may be operated by pulses ofcurrent. The current pulses need be of amplitude and duration justsufiicient to cause the rotor magnet to reverse its position. Once thepulse has passed, the rotor will hold its new display position until anew pulse of opposite polarity is applied to the coil, whereupon it willrotate to its other display position. Of course, a second oppositelywound coil may be disposed around the core and additional terminal pinsprovided for energizing this second coil. With two oppositely woundcoils, reversal of the rotor may be achieved with pulses of the samepolarity.

What is claimed is:

1. An electromagnetic indicator comprising:

a rotor support having a pair of spaced ears;

a rotor having oppositely polarized permanent magnet poles, said rotorbeing disposed between said ears;

said ears and rotor having cooperating means for releasably androtatably mounting said rotor to said cars so that said permanent magnetpoles reside in a common plane that extends tranversely of the axis ofrotation of said rotor;

first and second stop means on said rotor;

a magnetic pole piece extending along said common plane and transverselyof said axis of rotation, said pole piece extending close enough to saidrotor to intercept (a) said first stop means when said rotor is rotatedin a first direction and (b) said second stop means when said rotor isrotated in a second opposite direction, whereby to establish first andsecond limit positions respectively for said rotor; and

electromagnetic field generating means for magnetizing said pole pieceso as to magnetically influence said rotor to rotate to one or the otherof said limit positions.

2. An indicator according to claim I wherein said electromagnetic fieldgenerating means comprises:

a hollow bobbin surrounding a portion of said pole piece;

a coil of electrically conductive wire wound around said bobbin; and

terminal leads connected to the ends of said coil for coupling said coilto a source of electrical current, said ears being integral with saidbobbin.

3. An indicator according to claim 1 wherein said ears are resilient andsaid cooperating means are adapted to provide a detent connectionbetween said rotor and said ears.

4. An indicator according to claim 3 wherein said cooperating meanscomprises a pair of aligned pins on said rotor and a pair of alignedholes in said ears, said ears being spaced from one another so that theymust be spread apart by flexing in order to insert said pins in saidholes.

5.' An indicator according to claim 3 wherein said pins are integralparts of said rotor.

6. An indicator according to claim 5 wherein said rotor comprises twoparts secured together, with one of said pins formed integral with oneof said parts and the other of said pins formed integral with the otherof said parts.

7. An indicator according to claim 5 wherein said rotor has acircumferentially extending slot in its periphery, and furtherwherein-said first and second stop means are surfaces at the oppositeends of said slot and said pole piece extends into said slot.

8. An indicator according to claim I further including:

a plastic case enclosing said rotor, said ears, said pole piece and saidelectromagnetic field generating means;

said rotor having indicia and at least a portion of said plastic housingbeing transparent so as to render one portion of said rotor visible whensaid rotor is in said first limit position and a second portion of saidrotor visible when said rotor is in said second limit position.

9. An electromagnetic indicator comprising:

a one-piece plastic case open at one end and closed at its opposite end,said case being transparent at least at said opposite end;

a combined coil and rotor support means comprising a hollow bobbin witha pair of spaced ears at one end of said bobbin, said coil and supportmeans being disposed within said case with said ears located at saidopposite end of said case,

an elongate magnetic core member disposed within said bobbin, one end ofsaid core member projecting between said ears;

a rotor disposed between said ears, said rotor having two distinctindicia for indicating two different states of said indicator and apermanent magnet with salient magnetic poles at opposite sides of theaxis of rotation of said rotor; means rotatably mounting said rotor tosaid ears;

means for limiting rotation of said rotor between first and second limitpositions;

a coil of electrically conductive wire wound on said bobbin about saidcore member for producing when energized by an electric current amagnetic field that magnetizes said core member with a polaritydetermined by the direction of said current through said coil;

terminal leads connected to the ends of said coil for energizing saidcoil with current from a selected source of current, said terminal leadsprojecting out of said one end of said case; and

means sealing ofi said one end of said case.

10. An indicator according to claim 9 wherein said rotor mounting meanscomprises cooperating relatively rotatable detent means on said ears andsaid rotor, said detent means being adapted to permit removal of saidrotor by flexing said ears.

tion:

a member comprising a hollow bobbin and a rotor support;

a core of magnetic material within said bobbin;

a coil wound on said bobbin and surrounding at least part of said core;

a rotor rotatably mounted to said rotor support, said rotor beingdistinctively finished for visual indications of position and comprisinga permanent magnet, said permanent magnet being magnetically coupled tosaid core so as to produce rotation of said rotor upon a change in thepolarity of said core induced by energization of said coil; and

a housing in which said member and rotor are disposed, said housinghaving end and side windows for viewing the resented distinctive surfaceof the rotor.

12. An indicator according to claim 11 wherein:

said rotor support comprises a pair of spaced resilient ears formedintegral with one end of said bobbin, and a hole in each ear; andfurther wherein said rotor comprises two identical halves securedtogether, each of said halves being formed with a pin at one side, saidpins being mounted in the said holes in said ears.

1. An electromagnetic indicator comprising: a rotor support having apair of spaced ears; a rotor having oppositely polarized permanentmagnet poles, said rotor being disposed between said ears; said ears androtor having cooperating means for releasably and rotatably mountingsaid rotor to said ears so that said permanent magnet poles reside in acommon plane that extends tranversely of the axis of rotation of saidrotor; first and second stop means on said rotor; a magnetic pole pieceextending along said common plane and transversely of said axis ofrotation, said pole piece extending close enough to said rotor tointercept (a) said first stop means when said rotor is rotated in afirst direction and (b) said second stop means when said rotor isrotated in a second opposite direction, whereby to establish first andsecond limit positions respectively for said rotor; and electromagneticfield generating means for magnetizing said pole piece so as tomagnetically influence said rotor to rotate to one or the other of saidlimit positions.
 2. An indicator according to claim 1 wherein saidelectromagnetic field generating means comprises: a hollow bobbinsurrounding a portion of said pole piece; a coil of electricallyconductive wire wound around said bobbin; and terminal leads connectedto the ends of said coil for coupling said coil to a source ofelectrical current, said ears being integral with said bobbin.
 3. Anindicator according to claim 1 wherein said ears are resilient and saidcooperating means are adapted to provide a detent connection betweensaid rotor and said ears.
 4. An indicator according to claim 3 whereinsaid cooperating means comprises a pair of aligned pins on said rotorand a pair of aligned holes in said ears, said ears being spaced fromone another so that they must be spread apart by flexing in order toinsert said pins in said holes.
 5. An indicator according to claim 3wherein said pins are integral parts of said rotor.
 6. An indicatoraccording to claim 5 wherein said rotor comprises two parts securedtogether, with one of said pins formed integral with one of said partsand the other of said pins formed integral with the other of said parts.7. An indicator according to claim 5 wherein said rotor has acircumferentially extending slot in its periphery, and further whereinsaid first and second stop means are surfaces at the opposite ends ofsaid slot and said pole piece extends into said slot.
 8. An indicatoraccording to claim 1 further including: a plastic case enclosing saidrotor, said ears, said pole piece and said electromagnetic fieldgenerating means; said rotor having indicia and at least a portion ofsaid plastic housing being transparent so as to render one portion ofsaid rotor viSible when said rotor is in said first limit position and asecond portion of said rotor visible when said rotor is in said secondlimit position.
 9. An electromagnetic indicator comprising: a one-pieceplastic case open at one end and closed at its opposite end, said casebeing transparent at least at said opposite end; a combined coil androtor support means comprising a hollow bobbin with a pair of spacedears at one end of said bobbin, said coil and support means beingdisposed within said case with said ears located at said opposite end ofsaid case, an elongate magnetic core member disposed within said bobbin,one end of said core member projecting between said ears; a rotordisposed between said ears, said rotor having two distinct indicia forindicating two different states of said indicator and a permanent magnetwith salient magnetic poles at opposite sides of the axis of rotation ofsaid rotor; means rotatably mounting said rotor to said ears; means forlimiting rotation of said rotor between first and second limitpositions; a coil of electrically conductive wire wound on said bobbinabout said core member for producing when energized by an electriccurrent a magnetic field that magnetizes said core member with apolarity determined by the direction of said current through said coil;terminal leads connected to the ends of said coil for energizing saidcoil with current from a selected source of current, said terminal leadsprojecting out of said one end of said case; and means sealing off saidone end of said case.
 10. An indicator according to claim 9 wherein saidrotor mounting means comprises cooperating relatively rotatable detentmeans on said ears and said rotor, said detent means being adapted topermit removal of said rotor by flexing said ears.
 11. Anelectromagnetic indicator comprising in combination: a member comprisinga hollow bobbin and a rotor support; a core of magnetic material withinsaid bobbin; a coil wound on said bobbin and surrounding at least partof said core; a rotor rotatably mounted to said rotor support, saidrotor being distinctively finished for visual indications of positionand comprising a permanent magnet, said permanent magnet beingmagnetically coupled to said core so as to produce rotation of saidrotor upon a change in the polarity of said core induced by energizationof said coil; and a housing in which said member and rotor are disposed,said housing having end and side windows for viewing the presenteddistinctive surface of the rotor.
 12. An indicator according to claim 11wherein: said rotor support comprises a pair of spaced resilient earsformed integral with one end of said bobbin, and a hole in each ear; andfurther wherein said rotor comprises two identical halves securedtogether, each of said halves being formed with a pin at one side, saidpins being mounted in the said holes in said ears.